The wastegate and turbine housing JMTC just upgraded mine to are definitely a lot beefier and they seem to have worked all the kinks out of their products in the years since I originally bought my turbo from them. They've gone from only a few hundred customers maybe 3-4 years ago to thousands now, and they've really worked any issues out of their upgraded designs. I could feel the difference immediately, it just felt a lot smoother. What year did you get your S42? And is it ported and polished?
also, what kind of BOV/Recirc valve are you using?
Ive tried several and the only one that I would recommend for this turbo is the Forge Recirculating Valve (n18 version whether you're running n18 or n15). It cut nearly a half second off of my 0-60 from just that one mod. You just HAVE to make sure it's this exact version of their valve, because Forge has several different ones that all look similar but operate differently.
its a quieter valve than stock or any of the blow off type valves, but It keeps the boost up between shifts much better than anything I've tried (and I've had DV+, upgraded stock valve, Turbosmart, other Forge valves and several more).
It doesn't waste boost like the blow off type valves; only releasing boost when necessary. You won't get the swish sound, but the performance is well worth it. The s42hp is relatively quiet as far as turbos go as well, so don't be alarmed if you're not getting the same kind of turbo sounds you're used to.
Are you on a Manic tune or RPM Power?

also be REALLY careful with those "octane boosters". You're much better off just buying a can or blending your 93 at a pump with 101. If you can't find a pump, motorcycle and dirtbike/atv shops should have it in 5gallon barrels. You can order online also. A lot of 'octane boosters' can cause serious detonation, which is exactly the reason I use pure 101 only.
Pushing over 300whp i started using it mostly to reduce the risk of damaging detonation that causes pistons and rods to go.

quite true, the only thing with e85 is that it will work your fuel pump about 30% harder, leading to failure much sooner. I definitely wouldn't run full tanks of it, even if I was tuned for it, unless I had the necessary fueling system hardware. Actually, especially if I was tuned for it. You really NEED a special fuel system made to work for e85.
Obviously by blending it you're not taking as huge a risk, but the potential is still there for damage.
101 unleaded, or something like Torco 108 or VP MS109 unleaded race fuel would be better for blending, in my opinion. Definitely don't add anymore e85 to your blend than you're currently using. I know it's definitely a much cheaper option to get to a high octane than buying straight up unleaded race gas, but i think you'll find substituting Torco 108 or MS109 for your E85 should yield much smoother feeling results.
obviosuly the Mini ECU will adjust to whatever octane you put in the tank, but e85 and R56's just don't seem to get along as well as race fuel and R56's. Plus I don't know of anyone stateside who makes an e85 conversion kit for the r56.
I know people have tried, but so far I've only seen successful r53 e85 conversions, and it's easier for them because they don't have a HPFP to worry about.
E85 is a lot more dense, so it really comes down to the fuel system. E85 doesn't atomize as quickly or burn as completely as race fuel in an engine made for petrol, so you need to have a fueling system that can account for that. Once you've got a proper e85 system, it'll feel great, but you could be risking gunking up your stock fuel pump.

Looks like im gonna stArt collecting stage 2 parts soon 🤪

I recently spoke with Mario on the phone. What a cool dude! I’m doing this now as well. On his recommendation that I will need to do it for the tune he will be giving me. At the moment he said to use 2 gallons of E85 then fill the rest of the way up with supreme. This should put it right around 93 octane. So far without the tune yet, the car does seem just the tiniest bit more responsive, and just seems a bit happier on the higher octane mix than straight premium unleaded. When I first emailed Mario I was thinking about going for just a stage 1 Manic tune. But with my upgraded turbo and the few other minor things I’ve done like a catless DP, after spending about an hour on the phone with him he recommended I get the RPM stage 3. A bit different than was originally intending, lol. But after talking to him, it’s weird, but I totally trust this guy to go tinkering with my ECU! He has a way of conveying his knowledge and enthusiasm for what he’s doing that just makes you go “Yeah! Make my car better!” Lol. He is coming up north in a few weeks and is going to meet up with me personally here in the Pacific Northwest! That is so awesome. I told him initially about how I need the car and can’t really take the downtime to send my ECU off somewhere. He can make that work as well! I’m very impressed so far, and I haven’t even met him in person or gotten the tune yet. When he explained the difference between the Manic and RPM remapping, although having 3 maps to choose from would be a neat feature, I don’t think I would change it much. Mario was in agreement and was the first one to actually bring up the fact that most folks who get the SPS switch, just kind of toss it in the glove box after a while and stick with the map they like the best. Then when he told me that he is running the RPM tune on his own Countryman, well that pretty much did it for me. I didn’t feel like he was trying to upsell me or anything at all either. He just laid out the facts of how they would work to produce safe power with what I have. And I need stage 3 to get things optimized the way they should be. I was concerned about drivability going with that drastic of a tune righ off the bat. But after more questions, Mario assured me that the drivability will actually improve and that’s all I needed to hear! Lol.
I can’t wait to meet him in person and talk Minis while he reflashes my ECU and we change out the plugs real fast (I’m buying colder plugs from him too). I’m definitely nervous as well, as this is far and away the biggest change I’ll have made or will make to the car, but I feel kind of like a little kid who’s waiting for Christmas Day too! Ha ha!
How is the daily drivability of your guy’s RPM tunes? What can I expect to ...... well..... expect?

That’s great. It sounds like I’m going to be smiling a lot! Now I’ll need to be careful about watching my speed around town! It already likes to go faster than the speed limit if I’m not careful.
I was wondering if you still get the pops and burbles only in sport, like it is now, or if it just does it all the time with the tune? Going to be stage 3 RPM tune. I forgot to ask Mario about it. I will when he does my tune, but it seems like a goofy thing to contact him about, since I’m ok with it either way, just curious.

That’s good to know about TCS/DCS! Thanks. Mario saw the post and sent me a text to answer the pop question. You guys are right on with his customer service!

+1
I don’t have my tune yet, but it’s getting closer all the time. Although I cannot yet speak about the product, Mario’s customer service is terrific! I have been talking with him for a few weeks now at least, and he has been great about answering any stupid questions I come up with. Sometimes I text him one question and he calls me and we speak for like an hour on the phone! His knowledge comes through effortlessly when talking about these cars with him. Customer relations go a long way in my book ( I guess I’m getting old, lol) and Mario is hands down the tuner I trust. I don’t see many others on these forums using and backing up their products, much less making themselves available to anyone on here..... that says a lot!

You are gonna love it!!!!